Job M. Kibii

Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa

From Australopithecus to Homo Our genus Homo is thought to have evolved a little more than 2 million years ago from the earlier hominid Australopithecus. But there are few fossils that provide detailed information on this transition. Berger et al. (p. 195; see the cover) now describe two partial skeletons, including most of the skull, pelvis, and ankle, of a new species of Australopithecus that are informative. The skeletons were found in a cave in South Africa encased in sediments dated by Dirks et al. (p. 205) to about 1.8 to 1.9 million years ago. The fossils share many derived features with the earliest Homo species, including in its pelvis and smaller teeth, and imply that the transition to Homo was in stages. A new species of Australopithecus, about 1.9 million years old, shows many derived features with Homo, helping to reveal its evolution. Despite a rich African Plio-Pleistocene hominin fossil record, the ancestry of Homo and its relation to earlier australopithecines remain unresolved. Here we report on two partial skeletons with an age of 1.95 to 1.78 million years. The fossils were encased in cave deposits at the Malapa site in South Africa. The skeletons were found close together and are directly associated with craniodental remains. Together they represent a new species of Australopithecus that is probably descended from Australopithecus africanus. Combined craniodental and postcranial evidence demonstrates that this new species shares more derived features with early Homo than any other australopith species and thus might help reveal the ancestor of that genus.

Australopithecus sediba Hand Demonstrates Mosaic Evolution of Locomotor and Manipulative Abilities

The hand of Australopithecus sediba, a rare example in the hominid fossil record, shows short fingers and a long thumb consistent with improved precision gripping while retaining strength for climbing. Hand bones from a single individual with a clear taxonomic affiliation are scarce in the hominin fossil record, which has hampered understanding the evolution of manipulative abilities in hominins. Here we describe and analyze a nearly complete wrist and hand of an adult female [Malapa Hominin 2 (MH2)] Australopithecus sediba from Malapa, South Africa (1.977 million years ago). The hand presents a suite of Australopithecus-like features, such as a strong flexor apparatus associated with arboreal locomotion, and Homo-like features, such as a long thumb and short fingers associated with precision gripping and possibly stone tool production. Comparisons to other fossil hominins suggest that there were at least two distinct hand morphotypes around the Plio-Pleistocene transition. The MH2 fossils suggest that Au. sediba may represent a basal condition associated with early stone tool use and production.

Geological Setting and Age of Australopithecus sediba from Southern Africa

From Australopithecus to Homo Our genus Homo is thought to have evolved a little more than 2 million years ago from the earlier hominid Australopithecus. But there are few fossils that provide detailed information on this transition. Berger et al. (p. 195; see the cover) now describe two partial skeletons, including most of the skull, pelvis, and ankle, of a new species of Australopithecus that are informative. The skeletons were found in a cave in South Africa encased in sediments dated by Dirks et al. (p. 205) to about 1.8 to 1.9 million years ago. The fossils share many derived features with the earliest Homo species, including in its pelvis and smaller teeth, and imply that the transition to Homo was in stages. A new species of Australopithecus, about 1.9 million years old, shows many derived features with Homo, helping to reveal its evolution. We describe the geological, geochronological, geomorphological, and faunal context of the Malapa site and the fossils of Australopithecus sediba. The hominins occur with a macrofauna assemblage that existed in Africa between 2.36 and 1.50 million years ago (Ma). The fossils are encased in water-laid, clastic sediments that were deposited along the lower parts of what is now a deeply eroded cave system, immediately above a flowstone layer with a U-Pb date of 2.026 ± 0.021 Ma. The flowstone has a reversed paleomagnetic signature and the overlying hominin-bearing sediments are of normal polarity, indicating deposition during the 1.95- to 1.78-Ma Olduvai Subchron. The two hominin specimens were buried together in a single debris flow that lithified soon after deposition in a phreatic environment inaccessible to scavengers.

A Partial Pelvis of Australopithecus sediba

Although it had a small brain and skull, Australopithecus sediba shows some human-like features in its reconstructed pelvis. The fossil record of the hominin pelvis reflects important evolutionary changes in locomotion and parturition. The partial pelves of two individuals of Australopithecus sediba were reconstructed from previously reported finds and new material. These remains share some features with australopiths, such as large biacetabular diameter, small sacral and coxal joints, and long pubic rami. The specimens also share derived features with Homo, including more vertically oriented and sigmoid-shaped iliac blades, greater robusticity of the iliac body, sinusoidal anterior iliac borders, shortened ischia, and more superiorly oriented pubic rami. These derived features appear in a species with a small adult brain size, suggesting that the birthing of larger-brained babies was not driving the evolution of the pelvis at this time.

Papio Cranium from the Hominin-Bearing Site of Malapa: Implications for the Evolution of Modern Baboon Cranial Morphology and South African Plio-Pleistocene Biochronology.

A new partial cranium (UW 88-886) of the Plio-Pleistocene baboon Papio angusticeps from Malapa is identified, described and discussed. UW 88-886 represents the only non-hominin primate yet recovered from Malapa and is important both in the context of baboon evolution as well as South African hominin site biochronology. The new specimen may represent the first appearance of modern baboon anatomy and coincides almost perfectly with molecular divergence date estimates for the origin of the modern P. hamadryas radiation. The fact that the Malapa specimen is dated between ~2.026–2.36 million years ago (Ma) also has implications for the biochronology of other South African Plio-Pleistocene sites where P. angusticeps is found.

A hominin scaphoid from Sterkfontein, Member 4: morphological description and first comparative phenetic 3D analyses.

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Morphometric variations of the 7th cervical vertebrae of Zulu, White, and Colored South Africans.

e see front matter Published by Elsevie doi:10.1016/j.jhevol.2011.06.001 Since the discovery of the Taung child and the naming of the genus Australopithecus (Dart, 1925), South African sites have produced a considerable array of hominin1 fossils. However, one anatomical region that is substantially under-represented in the South African hominin fossil record is the wrist, which is currently represented by only two carpal bones: a right capitate (TM 1526) and a right triquetrum (SKX 3498). The capitate, discovered by Robert Broom during the late 1930s in bone breccia fromMember 4 at Sterkfontein, is typically referred to Australopithecus africanus (Broom and Schepers, 1946). The triquetrum was recovered from Member 2 at Swartkrans during the 1979e1986 excavations but has not been attributed to a particular hominin taxon (Susman, 1988; Kivell, 2011). Although SKX 3498 is broadly similar to that of African apes and humans (Kivell, 2011), TM 1526 shows a mix of primitive and derived features similar to that observed in several Australopithecus capitates from East Africa as well as the capitate of Homo floresiensis from Flores, Indonesia (Broom and Schepers, 1946; Lewis, 1973; Bush et al., 1982; McHenry, 1983; Ward et al., 1999a,b, 2001; Tocheri et al., 2007, 2008). Recently, a well-preserved hominin scaphoid was identified by one of us (JMK) while analyzing faunal remains from Sterkfontein (Kibii, 2004). This fossil carpal bone is accessioned as Stw 618 and is

Taphonomy of a novel small carnivore: experimental analysis of honey badger (Mellivora capensis) modifications on leporid prey

The 7th cervical vertebrae of 240 cadavers of South African Zulu, White, and Colored population groups were examined to determine morphometric variation. White and Colored females had statistically significant narrower cervical anteroposterior diameters than their male counterparts, whereas no statistically significant difference between sexes of the Zulu population group was observed in this variable. In addition, although Zulu and Colored females had statistically significant narrower cervical transverse diameters than their male counterparts, there was no statistically significant variation between South African white males and females in this respect. The findings indicate that sexual dimorphism is more apparent in the vertebral centrum, across the three population groups, where males had significantly larger dimensions in centrum anteroposterior diameter, height, and width than their female counterparts. The study further reveals that sexual dimorphism is more apparent when one compares aspects of the 7th cervical vertebra between sexes within the same population group. Overall, the dimensions of the various variates of the vertebra are substantially smaller in women than in men. The smaller dimensions, particularly of the centrum, may be the result of lower skeletal mass in women and render them more vulnerable to fractures resulting from compression forces. Clin. Anat. 23:399–406, 2010.

Experimental study of bone modification by captive caracal (Caracal caracal); a model for fossil assemblage analysis

The honey badger is a widespread, but understudied African carnivore, with high potential as a bone accumulator in cave and fossil deposits. This study serves as the first investigation into the taphonomic modifications of this species when feeding on small to medium-sized prey. Domestic rabbit (Oryctolagus cunniculus) carcasses where fed experimentally to a breeding pair of captive honey badgers housed at the Johannesburg Zoo. Bones from the feeding refuse and the carnivore scats were analysed for anatomical composition, fragmentation patterns, tooth marks and digestion. The results were compared with feeding studies with various small carnivores on leporid prey. Honey badgers preferentially opened their prey at the belly and focussed their feeding on nutritionally high-yield soft parts, often discarding low-yield parts like distal appendages, crania and the skins. Bones from the refuse assemblage were often complete and unmodified but stripped of flesh. Bones from the scat assemblage displayed very high fragmentation, light digestive modification and high numbers of tooth marked bones. This latter character was particularly diagnostic for the honey badger. This study investigates a carnivore that has received little interest and shows the high potential of this carnivore to act as a bone accumulator. Further taphonomic research into this species will greatly enhance our understanding of this species and its activity in the fossil record.